The invention relates to an air nozzle for pneumatic false-twist spinning having several parts arranged behind one another in moving direction of the yarn, each part forming a section of a yarn duct and one of these parts being provided with compressed-air ducts leading into the yarn duct.
In a known air nozzle of the initially mentioned type (DE-A 37 32 708), the comPressed-air ducts are provided between the surfaces, which rest against one another, of two parts following one another. The inside diameters of the parts increase step-by-step in moving direction of the yarn.
In another known air nozzle (DE-A 33 01 652), the compressed-air ducts are worked into a part as round bores. Also in this construction, a part with a larger inside diameter connects to the parts having the mouths of the compressed-air ducts.
On the basis of JP-B 61-58 571, which shows an air nozzle in a very schematic position, it is known to arrange in a central section of the nozzle, which contains the compressed-air ducts, inserts in moving direction of the yarn in front of and behind the compressed-air ducts which have a smaller diameter than the area of the compressed-air ducts.
An object of the invention is to develop the part which contains the compressed-air ducts in such a manner that, if possible, this part is subjected to no wear.
This object is achieved in that, in moving direction of the yarn, behind the part containing the compressed-air ducts, a part is arranged which consists of a material which is harder and more resistant to wear than the preceding part and has a smaller inside diameter than that part.
Since the part with the compressed-air ducts has a larger inside diameter than the part which follows, it is subjected to no or practically no contact with the yarns which are moving through, so that no significant wear occurs, particularly in the area of the mouths of the compressed-air ducts. In addition, the part which follows is wear-resistant so that the overall wear can be reduced. The part having the compressed-air ducts is made of a softer material, so that the mounting of the compressed-air ducts does not become more difficult.
In a further development of certain preferred embodiments of the invention, it is provided that the part which precedes the part containing the compressed-air ducts is made of a harder and more wear-resistant material and has a smaller diameter. By means of this development, it is also ensured that a contact of the part having the compressed-air ducts with the fiber material is largely avoided, while, in addition, the inlet area is also more protected with respect to wear.
In a further development of certain preferred embodiments of the invention, it is provided that the part in front of and/or the part behind the part containing the compressed-air ducts is made of a ceramic material. As a result, a particularly good protection is obtained with respect to wear.
In a further development of certain preferred embodiments of the invention, it is provided that the compressed-air ducts are drilled into the corresponding part with a round cross-section. By means of this drilling of round ducts, high-precision cross-sections are obtained which are advantageous with respect to the flow. In this case, it is advantageous for the compressed-air ducts to be aligned vertically with respect to the moving direction of the yarn. This vertical alignment with respect to the moving direction of the yarn permits a precise drilling which is particularly significant if the compressed-air ducts are arranged as tangentially as possible with respect to the inside diameter.
In a further development of certain preferred embodiments of the invention, it is provided that the parts are joined together with a housing part as a preassembled constructional unit. This ensures that, during the operation of the spinning machine, the air nozzle is not displaced and possibly damaged by improper handling in the area of the compressed-air ducts.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.